By Steve Jones, MIDEL

High-speed rail can change the world. It can open up opportunities for places previously closed off from economic centres, revitalise cities and even protect the environment by providing a viable alternative to certain flight routes.

China is a shining example. Since 2004 the development of its railway networks has taken place on a scale beyond anything that the world has seen before, hand-in-hand with economic expansion.

China’s high-speed railway network is by far the longest in the world. By June 2018 it extended to 22 of the country’s 29 provinces, stood at a whopping 26,869 kilometres (16,696 miles) in length and made up around 64% of the world’s high-speed rail tracks. Further plans to increase this to 38,000 km by the early 2020s are well underway.

China is also seeking to rebalance its growth geographically to encourage growth and enhance economic inclusion.

After three decades of rapid development in its Eastern Provinces, the development of the Central and Western Provinces then became a priority of the country’s policy makers, with improved connectivity crucial in doing so. For example, the less developed province of Guizhou was connected by rail to the advanced province of Guangdong, opening new opportunities for all.

It’s not just the length of the infrastructure that has so staggered the world but its speed. Much of the new track is designed to support high speed rolling stock not dissimilar to the trains that we will see introduced on the UK’s new HS2 line when it opens in 2026.

But while in China top speeds will regularly reach up to 350 km/hour (217 mph) and generally don’t run below 250 km/h, or 124 mph, HS2 won’t run above 320 km/h, unless amendments are made to the current plans.

photo: MIDEL

A good example to illustrate the difference high speed rolling stock can make to a journey is to consider the commute between the two cities of Beijing and Xi’an, which is around 746 miles. This journey takes approximately two hours by air, 11 hours by car, and used to take anything from 11.5 hours to 17.5 hours by train. On the fastest “bullet train”, the journey now takes an incredible 4.5 hours.

But China is only one example of this global phenomenon. From France’s long-established TGV (Train à Grande Vitesse) to the planned California High-Speed Rail system, high-speed rail is capturing imaginations around the world.

In order to implement such a fundamental shift in transport expectations, rolling stock manufacturers such as Alstom, Bombardier and Siemens are increasingly taking an “Apple” style approach to technology development. Rather than modifying or maximising the potential of existing technologies, they are increasingly challenging and collaborating with partners to create new solutions and keep up with the unrelenting pace of change.

The unheralded heroIt is within this context that a rather unlikely hero of modern transportation has emerged. Synthetic ester transformer fluid, such as the MIDEL brand manufactured and developed in the UK, is the lynch pin allowing this expedited advancement for high speed networks around the world.

The physics is fairly simple, an electrified train takes its power from overhead power lines, via an on-board transformer. Faster trains need more power, more power means more heat generated through the transformer. Of course, more heat and strain on the transformer inevitably increases the risk of wear and tear, malfunction and the potential for on-board fires.

Demand for electricity on trains has also soared in recent times in line with customer preference for ancillaries such as wi-fi, power sockets for laptops and phones, enhanced catering and lighting. This is particularly true as developing societies become more affluent and their travellers’ requirements more exacting.

As a result, multiple transformers per carriage are now required where one per train was once enough. Electrical Multiple Units are now in common use around the world – train carriages, each one powered by electricity, which together form one train. Even in these cases, where many transformers are used and distributed throughout the rolling stock, a significant reduction in power would occur if even one of the transformers on the train were to fail, meaning a reduction in speed and acceleration.

MIDEL 7131 is a synthetic ester dielectric fluid, which means that in addition to increased fire safety margins and stability, it is biodegradable (photo: MIDEL)

All these factors increase the need for light, adaptable, safe, reliable systems that remain stable and cool under considerable stresses. Until recently it was only possible to do so while trains travelled at speeds far slower than current high-speed fleets.

This extra performance cannot come at the cost of extra weight or size, as this would likely impinge the efficiency of the train. So, solutions that keep the size of the transformers the same, or even smaller, while delivering gains in power output are what was required.

What is it?Liquid-filled transformers use dielectric, insulating fluids in order to regulate temperature, and therefore stability and reliability. These fluids can take many forms but as well as being excellent electrical insulators, such fluids also need good thermal conductivity in order to function. Up to now mineral oil has been the fluid of choice; however, this fluid has a fire point of around 160° C, which, given the operating temperatures of transformers when in use, means fire could occur if any leakage were to happen.

Fortunately, there are alternatives. MIDEL synthetic ester fluid was developed specifically to be used as a transformer dielectric fluid. Its robust characteristics meant it was quickly adapted for use across many sectors and applications. Crucially, it has a very low pour point and proven oxidation stability, making it suitable for liquid operating temperatures between -56° C all the way through to extremely high ambient temperatures. In addition, its composition means that on top of vastly increased fire safety margins and stability, it is biodegradable. This gives a lower environmental impact in the event where the liquid is spilled or leaks from the train’s on-board transformer.

In short, this means that operating at extremely high speeds, on tracks often elevated to navigate challenging terrain, across multiple fluctuations in power supply and load, now became possible.

The future’s futureThe use of this particular synthetic ester continues to grow in rolling stock around the world, from Europe, to the US, Russia and Asia.

The fluid’s chemical composition continues to prompt and facilitate innovation in transformer manufacturers, who look to design and build smaller and slimmer transformers that can perform safely under fluctuating loads.

Right now, it seems, the only thing slowing the uptake of MIDEL synthetic ester fluid is the imagination of the high-speed world around it.

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